A 220‑lb patient with a blood glucose of 560 mg/dL, how much Humalog (insulin lispro) should be given?

Correction Insulin Dosing for Acute Hyperglycemia

For a 220-lb (100-kg) patient with blood glucose of 560 mg/dL, administer 4 units of Humalog immediately as a correction dose, then urgently establish a scheduled basal-bolus insulin regimen because this degree of hyperglycemia indicates complete inadequacy of the current treatment approach.

Immediate Correction Dose

• Give 4 units of Humalog (insulin lispro) subcutaneously right now for blood glucose >350 mg/dL, according to the simplified correction protocol recommended by the American Diabetes Association 1.
• Recheck capillary blood glucose in 1–2 hours after the correction dose 1.
• If glucose remains >300 mg/dL after 2 hours, administer an additional correction dose and investigate underlying causes (infection, medication non-adherence, DKA) 1.

Critical Assessment Required

• Check for diabetic ketoacidosis (DKA) immediately if the patient has type 1 diabetes or is insulin-dependent, especially if accompanied by nausea, vomiting, abdominal pain, or altered mental status 1, 2.
• Obtain urine or blood ketones, as glucose of 560 mg/dL with ketones constitutes a medical emergency requiring IV insulin infusion 2.
• If ketonuria is present or blood ketones ≥0.5 mmol/L, this patient requires hospitalization and continuous IV insulin, not subcutaneous correction doses 2.

Why This Single Correction Dose Is Insufficient

• A blood glucose of 560 mg/dL signals complete failure of the current insulin regimen, not merely a need for correction 1.
• Sliding-scale insulin used as monotherapy is explicitly condemned by all major diabetes guidelines and shown to be ineffective—only 38% of patients achieve mean glucose <140 mg/dL with sliding-scale alone versus 68% with scheduled basal-bolus therapy 1.
• This patient requires immediate transition to a scheduled basal-bolus insulin regimen, not reliance on correction doses 1.

Establishing a Proper Insulin Regimen

Calculate Total Daily Insulin Requirement

• For severe hyperglycemia (glucose >300 mg/dL), start with 0.3–0.5 units/kg/day as total daily dose 1.
• For this 100-kg patient, that equals 30–50 units total daily 1.

Basal-Bolus Split

• Give 50% as basal insulin (glargine, detemir, or degludec) once daily = 15–25 units 1.
• Give 50% as prandial insulin (Humalog) divided among three meals = 5–8 units before each meal 1.

Titration Protocol

• Increase basal insulin by 4 units every 3 days if fasting glucose ≥180 mg/dL 1.
• Increase prandial insulin by 1–2 units every 3 days based on 2-hour postprandial glucose readings 1.
• Target fasting glucose 80–130 mg/dL and postprandial glucose <180 mg/dL 1.

Timing of Humalog Administration

• Administer Humalog 0–15 minutes before meals for optimal postprandial glucose control 1, 3.
• Never give rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1.

Foundation Therapy

• Continue metformin at maximum tolerated dose (up to 2000–2550 mg daily) unless contraindicated, as the combination of metformin and insulin provides superior glycemic control with reduced insulin requirements and less weight gain 1.
• Consider discontinuing sulfonylureas when starting intensive insulin therapy to reduce hypoglycemia risk 1.

Common Pitfalls to Avoid

• Do not rely solely on correction doses when blood glucose is consistently >250 mg/dL—this indicates the need for scheduled basal and prandial insulin 1.
• Do not delay transition to scheduled insulin when glucose values are in the 500s, as this prolongs exposure to severe hyperglycemia and increases complication risk 1.
• Do not assume a 4-unit correction is adequate for glucose of 560 mg/dL; such dosing indicates fundamental under-treatment of the underlying insulin deficiency 1.

When to Seek Emergency Care

• Presence of ketonuria (≥trace) or blood ketones ≥0.5 mmol/L 2.
• Clinical signs of DKA: nausea, vomiting, abdominal pain, altered mental status, or Kussmaul respirations 2.
• Persistent glucose >300 mg/dL despite two correction doses 1.
• Inability to take oral fluids or evidence of dehydration 2.

Expected Outcomes with Proper Therapy

• With appropriate basal-bolus therapy at weight-based dosing, 68% of patients achieve mean blood glucose <140 mg/dL 1.
• HbA1c reduction of 2–3% is achievable over 3–6 months with proper insulin intensification 1.
• No increased hypoglycemia risk when basal-bolus therapy is properly implemented compared to sliding-scale approaches 1.